1. Field of the Invention
This invention relates to a five(5)-phase stepping motor driven by driving signals in five phases.
2. Description of the Prior Art
As conventional circuits for driving the 5-phase stepping motor, those of standard drive, pentagon drive, and star drive type have been proposed and are now in use. Because of difficulties in performance of half-step driving depending on 4- or 5-phase excitation by the pentagon and star drives, the standard drive is mainly used for this performance.
FIG. 1 is a diagram showing the standard drive for driving a conventional 5-phase stepping motor.
In FIG. 1, the reference numerals 1 to 5 indicate five coils of five phases A to E, respectively, wound around stator poles of the 5-phase stepping motor. The coils 1 to 5 of respective phases are driven in a way that some are driven in the same phase and others in the reverse phase. The power source 7 impacts exciting current to each of coils of all phases.
As apparent from this diagram, such a 5-phase stepping motor as above is provided with 10 input terminals corresponding to five coils, thereby requiring complicated wiring and hands. In a circuit for driving the 5-phase stepping motor, four transistors are used for coils of respective phases and, therefore, twenty transistors in total must be prepared for composing output steps. As a result, there arise such problems as an increase in heat generation in output steps, increase in the size of the output step, and complexity of control circuit for controlling the output step.
A structure in which coils 1 to 5 of respective phases are excited in parallel makes it necessary to adapt the power source 7 to supply electric current in quantity four to five times larger than that of the rated current (current of allowable quantity to be flowed into coils of all phases) for the motor correspondingly to 4-5 phase excitation. Accordingly, the stepping motor of such structure as above requires a power source of large current capacity.